WASHINGTON — President Barack Obama’s national security team argued Wednesday to keep its sweeping domestic surveillance powers intact, even as it acknowledged some limitations appear inevitable.

Facing unexpectedly harsh opposition from both parties over a once-secret program that sweeps up the phone records of every American, the Obama administration said it wanted to work with lawmakers who seemed intent on putting limits on that authority.

“We are open to re-evaluating this program in ways that can perhaps provide greater confidence and public trust that this is in fact a program that achieves both privacy protections and national security,” Robert Litt, counsel to the Office of the Director of National Intelligence, told skeptical members of the Senate Judiciary Committee.

To that end, the administration declassified documents about the telephone program. But the documents revealed no legal analysis that underpinned the widespread surveillance. And the redacted documents show only in broad strokes how NSA officials use the data.

For the first time, however, the government acknowledged publicly that using what it calls “hop analysis,” it can analyze the phone calls of millions of Americans in the hunt for just one suspected terrorist. That’s because NSA analysts can look at not just a suspect’s phone records, but also the records of everyone he calls, everyone who calls those people and everyone who calls those people.

If the average person calls 40 unique people, three-hop analysis could allow the government to mine the records of 2.5 million Americans when investigating one suspected terrorist.

“What’s being described as a very narrow program is really a very broad program,” said Sen. Richard Durbin of Illinois, the No. 2 Democrat in the Senate.

John Inglis, the NSA’s deputy director, conceded the point but said, in practice, such broad analysis was rare. ”We have to compare the theory to the practice,” he said.

The hearing came one week after a surprisingly close vote in the House that would have killed the phone surveillance program. It barely survived, but lawmakers promised that change was coming.

On Wednesday, the national security establishment sought to reassure Congress that its surveillance powers were rigorously monitored and narrowly crafted while simultaneously leaving open the possibility of some new limitations.

This newest privacy-vs.- security debate was touched off when former government contract systems analyst Edward Snowden leaked classified documents exposing National Security Agency programs that store years of phone records on every American. That revelation prompted the most significant reconsideration yet of the vast surveillance powers Congress granted the president after 9/11.

The administration intended to keep the telephone program a secret forever and, for more than a decade, few in Congress showed any interest in reining in the surveillance. Snowden’s leaks abruptly changed the calculus on Capitol Hill.

We have a lot of good information out there that helps the American public understand these programs, but it all came out late. It all came out in response to a leaker

“We have a lot of good information out there that helps the American public understand these programs, but it all came out late,” Sen. Sheldon Whitehouse, D-R.I., said in a rebuke of government secrecy. “It all came out in response to a leaker. There was no organized plan for how we rationally declassify this so that the American people can participate in the debate.”

The telephone program is authorized under a provision of the USA Patriot Act, which Congress hurriedly passed after 9/11.

The Obama administration says phone records are the only records being collecting in bulk under that law, but it has left open the ability to create similar databases of people’s credit card transactions, hotel records and Internet searches.

Several Democrats promised bills that would provide tighter controls or more transparency. Proposals include eliminating the FBI’s ability to seize data without a court order, changing the way judges are appointed to the surveillance court, and appointing an attorney to argue against the government in secret proceedings before that court. Another would force the government to reveal how many Americans have had their information swept up in surveillance.